1. Spiranes exhibit optical isomerism because of restricted rotation.
a) True
b) False
Explanation: Spiranes exhibit optical isomerism because of restricted rotation. They cannot rotate about any axis.
2. Which of the following is not optically active compound?
a) 1,7- Dicarboxylic spirocycloheptane
b) 1,3- Diphenyl propadiene
c) Meso-tartaric acid
d) Glyceraldehyde
Explanation: Meso-tartaric acid is an optically inactive molecule with a chiral carbon atom. It is a special case of optical activity.
3. The reaction which gives exclusively one of several possible isomeric products is called ____________
a) Dynamicselective
b) Stereoselective
c) Regioselective
d) Stereospecific
Explanation: The reaction which gives exclusively one of several possible isomeric products is called regioselective reaction. Regioselectivity is the preference of one direction of chemical bond making or breaking over all other possible directions.
4. The reaction that yields predominantly one enantiomer of a possible pair is called ____________
a) Dynamicselective
b) Stereoselective
c) Regioselective
d) Stereospecific
Explanation: The reaction that yields predominantly one enantiomer of a possible pair is called stereoselective reaction. Stereoselectivity is the property of a chemical reaction in which a single reactant forms an unequal mixture of stereo isomers during the non-stereo specific creation of a new stereo center or during the non-stereo specific transformation of a pre-existing one.
5. Stereoselectivity can be exhibited in various degrees.
a) True
b) False
Explanation: Stereoselectivity can be exhibited in various degrees like completely stereoselective, highly stereoselective, moderately stereoselective and so on.
6. The reaction in which stereochemically different molecules react differently is called ____________
a) Dynamicselective
b) Stereoselective
c) Regioselective
d) Stereospecific
Explanation: The reaction in which stereochemically different molecules react differently is called stereospecific reaction. Stereospecificity is the property of a reaction mechanism that leads to different stereo isomeric reaction products from different stereo isomeric reactants, or which operates on only one of the stereo isomers.
7. Which of the following is an example of regioselective reaction?
a) Debromination of 2,3- dibromobutane
b) 2-bromo octane with sodium hydroxide
c) Addition of HI to propylene
d) Debromination of meso dibromobutane
Explanation: Addition of HI to propylene is an example of regioselective reaction. Regioselectivity is the preference of one direction of chemical bond making or breaking over all other possible directions.
8. Reaction of (±) 2,3- dibromobutane is slower than meso in which the two methyl groups are ____________
a) Skew
b) Anti
c) Gauche
d) Partially eclipsed
Explanation: Reaction of (±) 2,3- dibromobutane is slower than meso due to higher transition state in which the two methyl groups are partially eclipsed.
9. Dynamic stereochemistry helps in correlating conformation and reactivity and in stereoselective synthesis.
a) True
b) False
Explanation: Dynamic stereochemistry helps in correlating conformation and reactivity and in stereoselective synthesis. Stereoselectivity is the property of a chemical reaction in which a single reactant forms an unequal mixture of stereo isomers during the non-stereo specific creation of a new stereo center
10. R – C = C – R reacts in the presence of lindlar catalyst to give a syn product. This is an example of ____________
a) Dynamicselective
b) Stereoselective
c) Regioselective
d) Stereospecific
Explanation: The above mentioned reaction is an example of stereoselective reaction. Stereoselectivity is the property of a chemical reaction in which a single reactant forms an unequal mixture of stereo isomers during the non-stereo specific creation of a new stereo center